81528191 has 4 divisors (see below), whose sum is σ = 81549384. Its totient is φ = 81507000.

The previous prime is 81528179. The next prime is 81528203. The reversal of 81528191 is 19182518.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (81528179) and next prime (81528203).

It is a cyclic number.

It is not a de Polignac number, because 81528191 - 2²² = 77333887 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81528101) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3020 + ... + 13121.

It is an arithmetic number, because the mean of its divisors is an integer number (20387346).

Almost surely, 2^81528191 is an apocalyptic number.

81528191 is a deficient number, since it is larger than the sum of its proper divisors (21193).

81528191 is a wasteful number, since it uses less digits than its factorization.

81528191 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21192.

The product of its digits is 5760, while the sum is 35.

The square root of 81528191 is about 9029.2962627217. The cubic root of 81528191 is about 433.6133073687.

The spelling of 81528191 in words is "eighty-one million, five hundred twenty-eight thousand, one hundred ninety-one".